Welding is commonly used to join many metal elements such as for example metal tubes. The metal welding may lead to various types of defects such as, for example, problems with cracking, inadequate penetration, inadequate coverage, problems with blow holing, oxidation or gaseous inclusions (blistering). In certain fields of application, such as for example and nonlimitingly the aerospace or aeronautic field, the quality and reliability of the weld must be guaranteed to be of the highest possible standard. In this context, it is advantageous to have at one's disposal a solution allowing the integrity of the welds produced on a metal tube to be inspected.
Conventionally, welds are inspected by X- or γ-ray radiology; however, this method has many drawbacks. A first drawback is the inspecting equipment. Specifically, these systems are heavy and bulky. During the radiography, very severe constraints are imposed by radiation protection: the item to be inspected must be transferred to a dedicated booth or personnel must be evacuated from a zone of consequent size. Once the radiography has been carried out, it is necessary to wait for the radio films to be developed before the inspection results can be interpreted. Regarding the interpretation of the results, locating defects on the periphery of the tubes is difficult. In addition, the detection of critical defects is dependent on the orientation of said defect.
Devices using an ultrasound inspecting method to verify the integrity of welds produced on tubes of large size, for example in the oil and gas field, do exist, but these devices are not easily transposable to the aeronautic industry.